This invention enables, for example, reduction of motion blur in a hold-type display device and reduce flicker in an impulse-type display device by a simple process. For this purpose, an LPF filters a frame of input image data (A[i]) to generate low-frequency image data (L). A subtractor and an adder generate high-frequency image data (SH). Another adder adds the low-frequency image data (L) from a delay circuit to subsequent low-frequency image data. A divider halves the sum to generate low-frequency averaged image data (SL). A switch alternately outputs the high-frequency image data (SH) and the low-frequency image data (SL) every time a frame of image data is input. As a result, the apparatus of this invention can generate output image data having a frame rate twice that of the input image data.